He founded a company called Fender Electric Instrument Manufacturing Company, which makes electric guitars, electric bass guitars, and electric guitar amplifiers. Leo Fender designed electric guitars which he called the Telecaster and the Stratocaster. Fender also designed the first bass guitar, which he called the Precision Bass. In the 1960s, Fender designed another bass guitar, which he called the Jazz Bass.
All of these instruments (the Telecaster, Stratocaster, Precision Bass, and the Jazz Bass) became popular. Fender Electric Instrument Manufacturing Company sold thousands and thousands of these instruments. Many rock and pop music bands from the 1960s to the 2000s use these electric guitars and electric bass guitars.